In therapy, a multiplicity of active compounds is used for the treatment and prophylaxis of all sorts of diseases. Drugs differ widely in their pharmacodynamic effects and clinical application, in penetrance, absorption and usual route of administration, in distribution among the body tissues and in disposition and mode of action.
Apart from the type of patient and the type of disease to be treated or to be prevented, the physicochemical properties of therapeutically active compounds determine to a great extent the preferred route of their admistration. In the development of drugs, the oral applicability thereof is usually an important selection criterium. For the majority of patients this is obviously the most convenient route for access of the drug to the systemic circulation. In order for a drug--administered via oral route--to act, it must first be absorbed before it is transported to the appropriate tissue or organ, where it may penetrate to the responding subcellular structure and may subsequently be metabolized, or where it may be bound, stored, or whatever is necessary to elicit a response or to alter ongoing processes. However, not always compounds which have been found to possess an advantageous therapeutic activity are also sufficiently absorbed in the gastrointestinal tract to display effective oral bioavailability.
Thus, one of the pivotal issues in drug design is to develop compounds which both show activity and good absorptive properties. An important area in which is actively sought for oral biavailability is the area of antithrombotic agents.